A child with Joubert syndrome (episodic hyperpnoea, abnormal eye-movements and ataxia) was followed from birth to eight years of age. Although severe mental retardation was suspected until approximately five years of age, unexpected and exceptional mental capacities were evident at later follow-up. Adequate testing and appropriate stimulation of children with such a severe early motor disorder are difficult, so they may give a false impression of mental retardation. The history of this child challenges the notion that mental retardation is part of Joubert syndrome.